Revision Notes-June Papers {PRACTICAL PAPERS}

8/4/2019 Revision Notes-June Papers {PRACTICAL PAPERS}

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June papers {PRACTICAL PAPERS}

Experiment determines the density of water by immersing a mass suspended by a spring into a beaker

of water.

Difficulty 1: E.g. hard to see the water surface/surface tension problems/refraction effects/parallaxerrors. .

Improvement 1:E.g. use calibrated beakers or masses/paper behind/mirror behind/travelling

microscope

Investigate how the force required maintaining equilibrium of a suspended mass depends on the

angle between the line of action of the force and the horizontal.

Difficulties that you had when making measurements of F and .

Indicator on the newton-meter sticks

Difficultly of too much compressive force to body of newton-meter when clamping

Difficult to position centre of protractor on knot

Protractorwobbles when being held by hand/wobbly hands

Parallax error when reading the scale on the protractor/newton-meter

Hard to align newton-meter parallel to line of action of F

Difficulty of ensuring AB is horizontal

Difficulty with zero on scale of newton-meter

Thick string makes measurement of angle hard

The centre of the knot could not be accurately located

The air-conditioning makes the string move/reason for moving string

Investigate the stability of a container of water as the height of water in the container ischanged.

Source of error in the measurement of d.Meniscus effects, shape of bottle leads to parallax

problems

Source of error in the measurement of . Parallax effects, difficult to keep head still, difficult

to move head with rule, difficult to judge point of toppling


2/10

Investigate the height to which a ball rises when it has been released from a stretched piece ofrubber.

Calculation to check proportionality: Two calculations of x2/h or ratio of x2 values and ratio of h values both

calculated.

Limitations: (A) Ruler not vertical. (B) locating the centre of the ball (when reading ruler). (C )Parallax

error. (D )Establishing when the ball is at its maximum displacement (E) only two displacements (are not

enough to validate the conclusion).(F) Difficulty in the release of the mass (reference to force/vertical

plane).

Improvements: (A) Sensible method to ensure ruler vertical. (B) Place the rule as close as possible to the

mass/mark the centre of the ball with mark or pointer/use the bottom/top of the ball. (C) Measure at

eye level/repeat to get eye in the right place/place the rule as close as possible to the mass. (D) Use

video camera (play back) frame by frame/slow motion/position sensor above or below. (E) Need awider range of displacements and plot a graph/find mean k. (F) Use a clamp/electromagnet to release

the mass.

Investigate how the rebound height h of a table-tennis ball is related to the height d fromwhich it is dropped

Ensure that the rebound height h was measured as accurately as possible: e.g. Use of set squares to

indicate height / repeat to refine position.

Improvement: (A )Take several d values and plot graph/compare e values (B) Use video and play back

slowly/position sensor (C) Method of reducing parallax problem (adjustable marker/drop many times torefine value of h/assistant to drop ball/ensure measurement taken at eye level) (D) Mechanical method

of release/hold ball against stop (E ) Method of making rule vertical (G) Use flat surface/turn off fans

Limitations: (A) Two sets of readings not enough (to draw valid conclusion)(B) Hard to judge rebound

height, with reason (C) Parallax (error in measuring h) (D) Difficult to release without applying a force

(E) Rule may not be vertical / perpendicular (F) Only cm divisions on rule (if borne out by readings)

(G) Inconsistent bounce


3/10

Investigate how the light detected by a light-dependent resistor (LDR) depends on thethickness of an absorber.

Problem (P) Solution (S)

Two readings not enough (to draw

a

conclusion).

Take many readings AND plot a

graph/find many values of k.

Alignment of cylinders/

alignment of LED/LDR.

Guide used; ruler/line on desk. /

Adjust LED/LDR to get max

voltage/method of fixing LED/LDR in

cylinder.

Difficult to hold all

together/voltage meter

fluctuates.

Stray light coming in/not light

tight/cylinders not sealed so let

light

enter tube/external light hits LDR

Method of fixing;

clamp/plasticine/tape.

Dark room/black cloth over

head/lights

off and blinds down/black box/black

tape.

Separation between LED and LDR

changes (as paper added).

Pre-slots in tube.

Roll out the modeling clay into a cylinder of length 4 cm. Wrap the 4 cm width of paperaround the cylinders length and fix with Sellotape

Calculation to check proportionality: Two calculations of t2/r or ratio of t2 values and ratio of r values

both calculated.

Limitations: A) - two sets of readings are not enough (to draw a conclusion) B) - difficult to make

accurate cylinder shape - cylinder radius/circumference varies C) - cylinder doesnt roll straight D) -

human reaction error (in timing) - measured time is very short not difficult to release cylinder and start

stopwatch together E) - difficult to judge end point

Improvements: A) - test many cylinders and plot a graph - test many cylinders and find many values of kB) - method of making more accurate cylinder D) - time over longer distance- use shallower angle ramp

- use light gates/pressure switches to measure time- use freeze-frame photography to measure time

- use motion sensor to measure time not just use video not repeated readings not just use

computer/data logger E) - mark distance with lines on ramp (to eliminate parallax) not use a pointer


4/10

Investigate the angle of tilt of a bottle when it contains different amounts of water .Sources of error or limitation. Improvements. Use of other apparatus

or

different procedures.

Two readings are not enough (to draw a

valid conclusion).

Take many (sets of) readings and plot a

graph of the results. Be clear NOT just

repeat readings.

Parallax error in measuring h/ . Get eye level/eye level perpendicular

(to

protractor lines, ruler scale or

meniscus).

Put scale onto bottle.

Difficult to measure height owing to

refraction/shape of bottle/thickness of

bottom not taken into account/ruler

does not

start at zero/cannot see meniscus

clearly.

Add dye/use ruler with a zero at the

start.

Difficulty in deciding the toppling point. Move by increments/hold with

newtonmeter

and tilt until F = 0/bottle on tilting ramp

idea.

Difficulty in measuring owing to

container

not perfectly right angled (curved) at

the

bottom/difficult to line up protractor/

horizontal line of protractor not on

table/

difficult to manipulate bottle and

measureangle/flexible container/shape of

bottle.

Make bottom square with

plasticine/use

protractor with horizontal line flush to

table

top/freestanding or clamped protractor


5/10

Investigate how the deflection at the centre of the loaded resistance wire of the arrangementshown in Fig. 2.1 depends on the current in the wire.

Ensure the accuracy of this reading of the height: Sensible practical detail such as position scale close to

mass holder, view horizontally, view at eye level, view perpendicular to scale, allow for zero error,

measure at several positions, use setsquare on bench to make ruler vertical. (Do not allow repeatedreadings).


6/10

Investigate how the time of swing of a tube depends on its length.


7/10

Investigate how the attractive force between two magnets depends on their separation.Difficult to determine this force accurately: Reaches maximum force suddenly (short time); no notice

given when releases

Explain how you have made this measurement as accurate as possible: Take repeats in different places

/ (account for) zero errors.


8/10

Investigate how the speed of a glass ball falling through oil depends on its size.


9/10

Investigate the effect of an electric current on a nearby magnet.


10/10

Investigate how the movement of a tube is affected by fluid friction.

Revision Notes-June Papers {PRACTICAL PAPERS}

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